Dr. Andreas Leemann:

I will first give some information about pyrrhotite. If there is pyrrhotite present in the aggregate used in the concrete, it will oxidise and create an internal sulphate attack. How fast this goes on depends on the reality of humidity. It is lower for the inner leaf than for the outer leaf. You cannot transfer the data or knowledge gained from the blocks to the foundations because the ratio between aggregate and cement content changes for foundations. There is a certain buffer of blocks to take some of the sulphur. However, it goes off stronger in blocks because there is more cement, and you can form more expansive ettringite and more thaumasite, which leads to strength loss. In principle, if it is in the concrete, pyrrhotite oxidation cannot be avoided. The question of gaining information as soon as possible to make the right decisions is not only for foundations; it is for any concrete of this quality that might have been used for stairs, garages or even bridges.